Manufacturing techniques: doing with ice what cannot be done with plastic

In some of Manhattan's better Japanese-staffed bars, like Tribeca's underground B-Flat, ice cubes are noticeably absent; ordering your scotch on the rocks gets you a large ice sphere. With less surface area than the same amount of ice rendered in cubes, a globe of ice will melt more slowly, keeping your drink cold without making it watery.

As an industrial designer, your correspondent couldn't help but notice the parting line on B-Flat's ice spheres; after all, it has to come out of a mold. But now a company called Taisin has come up with a clever device for making a perfect ice sphere with no parting line.

How does it work? You sandwich a large chunk of ice in between the two metal pieces pictured above. As the ice slowly melts, gravity brings the top half to close over the bottom half, enclosing what ice remains in its spherical cavity. Because the ice is in the process of melting into its new shape as the top closes, there's no parting line. Clever!

Other shapes are available as well; what you see at the bottom right of the photo is an ice soccer ball. (Don't ask, it's Japan.)

1 Comment

Transport Troubles in Trendy Tribeca?
"With less surface area than the same amount of ice rendered in cubes, a globe of ice will melt more slowly, keeping your drink cold without making it watery."
For starters, a perfect sphere has only 20% less surface area than a perfect cube. So it's rather silly on its face.
But it doesn't really make any sense in the most fundamental way. The rate of melting is going to be driven by the liquid temperature, i.e., the temperature gradient between the solid and liquid phases. No more ice will be melted than is necessary to reach the desired (near-freezing) temperature -- it's melting by demand.
Of course the cube will melt differently than a sphere, with a higher rate of melting at the corners at first, but it will still ultimately be driven by demand, by the liquid temperature. One might even make the argument that a cube is probably a more optimum shape: during the most transient phase (at the beginning), the liquid will reach near-freezing temperature more quickly with a cube than a sphere, but later in the (more steady-state) process, decrease in melting demand occurs simultaneously with an increase in the cube's sphericity (decrease in surface area). If you like a cold drink, and you don't want to wait, a cube is probably better -- while you're waiting for your drink to get cold with a sphere, you're also subject to more environmental heat load while you're waiting. That is, for the drink to get to a desired temperature, you will have diluted your drink more with a sphere than with a cube.
Obviously, the main variables that drive the rate of melting are the insulation characteristics of the glass, the ambient air temperature, and the temperature of the grubby little hand holding the drink.
But from a user-perspective, no matter what the shape is, drinkers will likely increase the heat transfer coefficient (and thus the rate of melting) by mixing a drink with a straw because they sense the rate of melting isn't high enough (the drink isn't cold enough).
So the process is really self-controlling, with additional user-control as desired.
But I nevertheless do like the aesthetics of a sphere.
Brian Dunaway
Chemical Engineer
Space Systems

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